The need to protect matter from harmful environmental influences arises in many areas of technology. One general solution to the problem comprises surrounding the substrate with an appropriate encapsulant.
For instance, when the matter to be protected comprises a joint or splice between electrical cables, such as multiconductor communications cables of the type ued in telephone systems, a prior art technique comprises providing an enclosure around the splice work, securing the enclosure to each cable entering the enclosure, and filling the enclosure with an insulating liquid curable encapsulant.
For example, U.S. Pat. No. 4,466,843 discloses a plastic liner that is placed around the splice work and secured to the cables, thereby forming an enclosure into which liquid encapsulant is poured under gravity. The encapsulant in the enclosure is then pressurized to some degree by wrapping ties, tape or the like, around the enclosure. In such a system, any encapsulant volume change subsequent to the wrapping can be expected to lead to a change in pressure. For instance, flow of encapsulant into voids within the splice work, or into the cables, decreases the effective volume of encapsulant within the enclosure, and results in a loss of pressure. Furthermore, in such a system, the splice work typically is compacted by the pressurizing means.
A new approach is disclosed by U.S. patent application Ser. No. 619,266 ('266), filed June 11, 1984 by F. J. Mullin et al (Mullin), co-assigned with this, and incorporated herein by reference. Mullin teaches forming an enclosure around the quantity of matter that is to be protected, filling the enclosure with a gelable (curable) liquid (the encapsulant), pressurizing the liquid, and providing means for maintaining pressure on the liquid at least until the liquid has solidified. In a preferred embodiment, an inner enclosure is formed around the splice by means of an elastomeric sheet, a rigid shell placed around the inner enclosure, and liquid encapsulant pumped into the inner enclosure until a predetermined pressure above ambient pressure is reached, with the elastomeric inner bag restrained by the rigid shell. Pressurization of the liquid encapsulant results, inter alia, in thorough penetration of the encapsulant into the splice work and in more complete expulsion of air from the enclosure. Enclosures of the Mullin type (referred to as the 2200 Series Closure System) are commercially available from AT&T Technologies, Inc.
A Mullin-type splice enclosure typically is better able to protect the splice from water damage than are other prior art enclosures. In particular, Mullin-type enclosures can withstand a substantially greater water head than can other prior art enclosures. However, we have found that the ability of Mullin-type splice enclosures to prevent water ingress at least in some instances decreases with time. In view of the importance of reliably excluding water from sensitive objects e.g., cable splices and optical fiber connectors, for long periods of time, an encapsulation system whose ability to withstand water ingress does not substantially decrease with time, and which is able to retain this ability under varying ambient conditions, would be of considerable interest. This application discloses such an encapsulation system.